Gaming Mode forces Stereo output over HDMI despite 5.1/7.1 configuration and working Desktop Mode
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Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 48/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Quiet
- Tech stack
- linux
- Domain
- operating-systems
Research direction
Start by comparing Gaming Mode with Desktop Mode while monitoring the active PipeWire sink alsa_output.pci-0000_04_00.1.hdmi-surround-extra2 and its 6-channel map. Reproduce with a docked Steam Deck and a surround-configured game; done means Gaming Mode sends active center, rear, and LFE channels over HDMI rather than only front left/right.
Written by the indexing model from the issue text.
Description
• Device: Steam Deck OLED
• SteamOS Version: 3.8.14 (BUILD_ID=20260703.1, stable)
• Audio Hardware: Steam Deck (original dock) → HDMI → Denon AVR → LG C3 OLED TV
Issue Description
Desktop Mode: Full 5.1 LPCM works correctly. The Denon AVR detects and shows a 5.1 container with all channels active during tests.
Gaming Mode: Games output only front left/right channels. The receiver still detects a 5.1 container, but its channel monitoring shows only front L/R active (no rear, center, or LFE activity) even when games are configured for surround sound.
Tested games: Cyberpunk 2077 and BioShock Remastered (set to 5.1).
Key Diagnostics (docked, 5.1 configured)
• Active PipeWire sink: alsa_output.pci-0000_04_00.1.hdmi-surround-extra2 (6ch, proper channel map FL/FR/RL/RR/FC/LFE).
• Receiver detects 5.1 but only front L/R carry audio in games.
• Full display modes available on DP-1 (including VRR Automatic).
Steps to Reproduce
- Dock the Deck and set 5.1 HDMI output in Desktop Mode (receiver shows 5.1 with all channels active).
- Switch to Gaming Mode.
- Launch a surround-supported game set to 5.1.
- Check receiver’s channel monitoring → only front L/R active.
Already Tried:
• PipeWire overrides.
• Audio service restarts.
• HDMI cable unplug/replug (fresh handshake).
• Different AVR inputs, CEC On/Off, proper power-on order.
Request
Gaming Mode should fully utilize the active 5.1 HDMI sink instead of restricting output to front L/R
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